Pyrazole-l-carboximidamides

The new pyrazolo[l,5-tf][l,3,5]benzoxadiazocine heterocyclic ring system 123 was prepared by cyclization of 4,5-dihydro-3-methyl-5-(2-hydroxyphenyl)-17/-pyrazole-l-carboximidamide with triethyl orthoformate. A reaction mechanism involving re-esterification of triethyl orthoformate with phenolic hydroxyl of the additional equivalent of hydroxyphenyl pyrazoline was proposed to explain the formation of the product with an additional guanidine moiety (Equation 17 <2002J(P1)1260>). 

Figure 1 Rates of Guanidinylation of Benzylamine with iV -Bis(tert-butoxycarbonyl)-S-methylisothiourea ( ), iV,iV -Bis(te/r-butoxycarbonyl)pyrazole-l-carboximidamide ( ), Ai,Ai -Bis(tert-butoxycarbonyl)thiourea in the Presence of the Mukaiyama Reagent ( ), and l,3-Bis(tert-butoxycarbonyl)-2-triflylguanidine ( )...

---